1. Technical Field
The present invention relates to a drive unit for a rotating electrical machine, and more particularly to an apparatus for supplying electrical current to a field winding and an armature winding of a rotating electrical machine which generates a field flux when a direct current is supplied to the field winding, and which generates a magnetic field that interacts with the field flux when an alternating current is supplied to an armature winding.
2. Related Art
An art related to a rotating electrical machine which generates a field flux when a direct current is supplied to a field winding and which generates a magnetic field that interacts with the field flux when an alternating current is supplied to an armature winding is disclosed in JP 6-351206 A (hereinafter referred to as the patent document 1). In the case of the rotating electrical machine in the patent document 1, as shown in FIGS. 19 and 20, a core 102 of a stator 101, which is an armature, is divided in two in the axial direction. Supposing that a part on one side of the divided core 102 is an N-pole side core 102a and a part on the other side of the core 102 is an S-pole side core 102b, as a matter of convenience, the N-pole side core 102a and the S-pole side core 102b are provided along the axial direction so as to sandwich an annular field winding 105 therebetween. The N-pole side core 102a and the S-pole side core 102b are mechanically and magnetically connected via a stator yoke 104 provided on an outer side thereof. An armature winding 103 is provided so as to bridge over the N-pole side core 102a and the S-pole side core 102b. Further, a core 112 of a rotor 111 is mechanically and magnetically connected to the rotor yoke 114 connected to a shaft 115. The rotor core 112 is in the form of a salient pole and has a partially protruded structure, and forms a salient pole portion 112a at a location other than where permanent magnets 113N and 113S are provided. The salient pole portion 112 may be separated into an N-pole side salient pole portion 112aN corresponding to the N-pole side core 102a and an S-pole side salient pole portion 112aS corresponding to the S-pole side core 102b. The N-pole permanent magnet 113N and the N-pole side salient pole portion 112aN are arranged alternately in the circumferential direction where the rotor 111 opposes the N-pole side core 102a, and the S-pole permanent magnet 113S and the S-pole side salient pole portion 112aS are arranged alternately in the circumferential direction where the rotor 111 opposes the S-pole side core 102b. Further, in the axial direction, the N-pole side salient pole portion 112aN and the S-pole permanent magnet 113S are arranged side by side, and the N-pole permanent magnet 113N and the S-pole side salient pole portion 112aS are arranged side by side.
In the rotating electrical machine according to the patent document 1, the field flux generated by the permanent magnets 113N, 113S passes through a closed magnetic path formed by the N-pole permanent magnet 113N, a gap, the N-pole side core 102a, the stator yoke 104, S-pole side core 102b, a gap, the S-pole permanent magnet 113S, the rotor core 112, the rotor yoke 114, the rotor core 112, and the N-pole permanent magnet 113N, in this order. Further, by supplying a direct current to the field winding 105, as shown in FIG. 19, a direct current flux (field flux) passes through a closed magnetic path formed by the stator yoke 104, the S-pole side core 102b, a gap, the S-pole side salient pole portion 112aS, the rotor core 112, the rotor yoke 114, the rotor core 112, the N-pole side salient pole portion 112aN, a gap, the N-pole side core 102a, and the stator yoke 104, in this order. At this time, the direction of the field flux is controllable by the direction of the direct current, and the amount of the field flux is controllable by the amount of the direct current. In the case where the direction of the field flux created by the direct current passing through the field winding 105 is in the same direction as the field flux created by the permanent magnets 113N, 113S, it is possible to perform field-weakening control since field flux linked to the armature winding 103 decreases compared to the case where direct current is not supplied to the field winding 105. On the other hand, in the case where the direction of the field flux created by the direct current passing through the field winding 105 is in the opposite direction to the field flux created by the permanent magnets 113N, 113S, it is possible to perform field-strengthening control since the field flux linked to the armature winding 103 increases compared to the case where direct current is not supplied to the field winding 105. Also, in the case where unidirectional direct current is supplied to the field winding 105, it is possible to perform field control (control of field flux linked to the armature winding 103) by controlling the amount of direct current supplied to the field winding 105.
FIG. 21 shows a configuration example of a drive circuit for supplying direct current to the field winding 105 in a rotating electrical machine in patent document 1. According to the example of configuration shown in 21, the drive circuit is a bridge-type chopper circuit (DC-DC converter), and it is possible to bidirectionally control the direct current supplied to the field winding 105 by switch controlling switching elements Tr1, Tr4 and switching elements Tr2, Tr3. Further, an inverter is used as a drive circuit for supplying alternating current to the armature winding 103, and it becomes possible to control the alternating current to be supplied to the armature winding 103 by switch controlling the switching element of the inverter.
In patent document 1, switching elements are necessary for both the drive circuit (DC-DC converter) for controlling the direct current to be supplied to the field winding 105 and the drive circuit (inverter) for controlling the alternating current to be supplied to the armature winding 103, respectively. Consequently, the number of switching elements necessary increases, resulting in an increased drive circuit cost.
The present invention has an advantage to realize low cost by reducing the number of switching elements used in controlling the current to be supplied to the field winding and the armature winding of a rotating electrical machine.